“I am shocked by the events of the past few days. Above all, I am stunned that misconduct on such a scale was possible in the Volkswagen Group,” Winterkorn said, according to a statement released on the company website. “As CEO I accept responsibility for the irregularities that have been found in diesel engines and have therefore requested the Supervisory Board to agree on terminating my function as CEO of the Volkswagen Group. I am doing this in the interests of the company even though I am not aware of any wrongdoing on my part.”

No replacement was immediately announced and the company’s supervisory board executive committee said it is “expecting further personnel consequences in the next days … all participants in these proceedings that has resulted in unmeasurable harm for Volkswagen, will be subject to the full consequences.”

The world’s largest carmaker faces fines of as much as $18 billion after the U.S. Environmental Protection Agency accused it of equipping its cars with software that detected when they were being tested, prompting the engine to temporarily reduce its emissions.

Volkswagen is being forced to recall almost half a million cars from the U.S. market and sales of its new models with the affected engine have been blocked.

The carmaker is also being investigated by European authorities, who want to be sure that the software fix, installed in 11 million cars, did not affect emissions tests in the EU.

Volkswagen said it is cooperating with a possible criminal probe by German authorities. The company, as well as some employees, could face possible criminal charges in the U.S.

Volkswagen shares fell by 40 percent on the Frankfurt stock exchange earlier this week, but were up by 6 percent on Wednesday. The company has already had to make a €6.5 billion provision against possible losses due to the investigation.

Volkswagen has not disputed the U.S. accusations, and earlier this week Winterkorn said he was “personally deeply sorry” for the situation and promised an investigation. Initially he had tried to hang on to his job — he has headed the company since 2007 — but his situation quickly became untenable.

German politicians, stunned by the scandal that has besmirched the country’s reputation for probity and engineering excellence, had been calling for ouster. France is demanding a European investigation, while Italy has launched its own probe.

The European Commission is also examining the situation.

“We are taking the matter very seriously,” said Lucia Caudet, a Commission spokeswoman. “We encourage all member states to carry out the necessary investigations and report back to the European Commission. We will discuss with them how best to coordinate these investigations.”

Volkswagen came under fire Wednesday in the European Parliament. MEPs called for tougher emissions controls in the EU, pointing out that the U.S. method of regulating and testing cars is more stringent than the European one. Volkswagen was caught in the U.S. despite diesel cars accounting for only about 1 percent of cars there, while they account for about half the cars on European roads.

“The current tests that check the driving emissions are not accurate, as the testing situation in a laboratory setting does not show the real driving conditions. There is an overdue need to reform the current test procedures,” said Matthias Groote, an MEP and environment spokesman for the Socialists and Democrats parliamentary group.